This marked the federal government’s first entry into the controversy that has occupied the federal courts continuously since Proposition 8 was challenged in a potentially landmark federal court case four years ago. President Obama, of course, has said that he favors allowing gays and lesbians to marry the persons they love, but his government has never sought explicitly to have the courts open marriage to those couples.

Rather than seeking a nationwide ruling to give same-sex couples marriage equality everywhere in the U.S., the administration’s lawyers offered a legal formula that would almost immediately make marriage available to gays and lesbians only in eight states–including California–that do not now allow it.

In addition to California, those states are Delaware, Hawaii, Illinois, New Jersey, Nevada, Oregon, and Rhode Island.

Considering what the administration might have proposed, that request qualified as quite modest. After all, the two same-sex couples who originated the challenge to Proposition 8 are asking the court to strike down marriage bans for such partners all across America, wherever that is still banned.

But, in order to get to the result the administration is seeking (the overturning of the 2008 ballot measure adopted in the Golden State), the new legal brief filed for the government suggested that the court adopt a sweeping new constitutional test that clearly has the potential to nullify laws of many kinds that treat gays and lesbians less favorably than straight people.

If the court were to mandate that test (which judges and lawyers call “heightened scrutiny”), that might one day mean the end of all bans on same-sex marriage, too. The administration was not seeking that result at this point, the brief made clear.

In fact, at one point in the new brief, the government’s attorneys said the court could decide the pending case on Proposition 8 without having to decide what the Constitution might require “under circumstances not present here.” That somewhat opaque phrase was meant to emphasize that the government was not asking the court to treat the basic right to marry, which the Constitution clearly protects, as an institution open to all same-sex couples.

In effect, the arguments made on Thursday offset the goal of advancing the cause of marriage equality to an important degree with a hesitation to push that goal from coast to coast. So, if the court were to follow the path suggested by the government, it very likely would mean that same-sex marriage would, for the time being, remain banned in 33 states (down from the current number, 41).

This arithmetic needs a bit of explaining. There are nine states out of the 50 that currently permit same-sex marriages, along with Washington, D.C. Such marriages are not allowed in the other 41. How would a court decision of the kind the government was suggesting get that number down to 33?

Eight states, including California, now provide all or nearly all of the benefits and legal rights of marriage to both same-sex couples and opposite-sex couples, so they are treated equally in that respect. But, in those states, only opposite-sex couples can go beyond their access to those benefits, and legally get married.

It is those eight states that are the target of the Obama administration’s legal challenge, even though it is framed as a challenge only to California’s Proposition 8. The argument that was made, in fact, is widely known by the phrase, “the eight-state solution” for same-sex marriage rights. The government was not proposing a “50-state solution.”

Under the government’s argument, the constitutional problem arose when the voters of California took away the marriage right for same-sex couples even as they left intact all of the marriage-like benefits for those couples.

When judged by a tough constitutional standard, or “heightened scrutiny,” that differing treatment of same-sex couples violates the Constitution’s guarantee of legal equality, under the 14th Amendment, the brief asserted.

Proposition 8, the brief contended, “forbids committed same-sex couples from solemnizing their union in marriage, and instead relegates them to a legal status–domestic partnership–distinct from marriage but identical to it in terms of the substantive rights and obligations under state law.”

The designation of marriage, the brief said, “confers a special validation of the relationship between two individuals and conveys a message to society that domestic partnerships or civil unions cannot match.”

Examining one by one the arguments that the sponsors of Proposition 8 make for that measure, the administration document found each of them insufficient to make up for the discrimination it argued is the result of that measure.

So, without any justification that would promote “any important governmental interest,” the brief said, Proposition 8 in the end emerges only as the product of “impermissible prejudice” against gays and lesbians.

Although the approach the administration has taken in this new filing is notably more modest than the gay rights community had hoped, and that the two same-sex California couples are still pursuing before the court, the administration’s argument does give the justices the option of deciding the pending case more narrowly, if they are not yet prepared to address same-sex marriage as a national issue.

What the brief did leave totally unmentioned, though, was that the court’s endorsement of the tough new constitutional test put forth by the administration would amount virtually to a very broad foundation for a historic new era of gay rights, going well beyond Proposition 8 and even beyond marriage.

Even though unacknowledged, that is the potential that could be seen between the lines of 32 pages of legal reasoning.